1. Field of the Invention
The present invention relates generally to a fixture for placing various electronic components (for example, a semiconductor bare chip, a ball grid array (BGA), a chip size package (CSP), or the like) on a circuit board. Particularly, the present invention relates to a fixture allowing an electronic component to be mounted easily using a flip chip technique and to be replaced easily. In addition, the present invention relates to a circuit board provided with such a fixture. The present invention also relates to a mounted body with an electronic component mounted using such a fixture and to a method of manufacturing the same.
2. Related Background Art
Recently, with the decrease in size and the increase in density of electronic equipment, there have been demands for flip chip mounting of semiconductor chips such as LSIs in a bare chip state not only in a field of industrial equipment but also extensively in consumer equipment.
In the flip chip mounting, there is a problem in that a semiconductor chip is bonded to a board with a resin adhesive called “an underfill” and therefore, repairs cannot be made once the semiconductor chip has been bonded. This is a hindrance in employing the flip chip mounting technique.
It is necessary for semiconductor chip manufacturers to deliver bare chips removed from circuit boards after the bare chip test or a burn-in test.
At present, there is no fixture practically used that allows a semiconductor chip to be placed on a circuit board in an easily removable manner using the flip chip technique. However, a fixture with a frame for fixing a CSP attached to a board on which contact pins with springs are arranged in a lattice-point form has been used experimentally as a fixture for a CSP in some cases.
JP 2(1990)-268491 A describes a method of replaceably mounting a double-pole chip component provided with electrodes at its both ends. The method is described as follows. Initially, a pair of inclined metal plates are attached to both ends of an insulator plate in a standing state and thus a stand is produced. Next, the stand is fixed onto a circuit board. In this process, a pair of electrodes formed on the circuit board and the pair of inclined metal plates are soldered to be electrically connected to each other, respectively. Then, while the electrodes at both ends of the double-pole chip component are allowed to contact with the pair of inclined metal plates, respectively, the double-pole chip component is held elastically between the pair of inclined metal plates. Thus, the electrodes of the double-pole chip component are electrically connected to the electrodes on the circuit board through the inclined metal plates. According to this method, even after being placed on the circuit board, the double-pole chip component can be removed from the circuit board easily by releasing of the elastic holding by the pair of inclined metal plates.
In addition, JP 3(1991)-241847 A describes a method of mounting a chip component with electrodes formed on its one surface. The method is described as follows. Initially, the electrodes of the chip component are aligned with electrodes on a circuit board, and then the chip component is placed face down on the circuit board. Next, a substantially U-shaped cap is put on the upper face (on which the electrodes are not formed) of the chip component with an elastic body layer interposed therebetween. Then, both foot parts of the cap are bonded to the circuit board. Thus, the chip component is pressed toward the circuit board by the cap with the elastic body layer interposed therebetween. Consequently, the chip component and the circuit board are electrically connected to each other.
However, the above-mentioned conventional mounting methods have the following problems, respectively.
The fixture for a CSP described above has a very large and complicated configuration. Therefore, it can be used for the burn-in test of semiconductor bare chips but cannot be used by any means for general electronic equipment in view of its shape and manufacturing cost. Furthermore, it also is difficult to apply the fixture to semiconductor chips with electrode pads arranged with a narrow pitch.
In the method of mounting a double-pole chip component described in JP 2(1990)-268491 A, the stand is used in which the pair of inclined metal plates are bonded to both ends of the insulator plate to be formed integrally therewith. In order to produce the stand, therefore, it is necessary to form the members made of different materials integrally. This makes the configuration of the stand complicated and thus results in a high manufacturing cost. In addition, the insulator plate is interposed between the chip component and the circuit board, and therefore the electrodes of the chip component and the electrodes on the circuit board are electrically connected to each other through the pair of inclined metal plates. This causes deterioration in properties such as a high frequency property. Furthermore, this mounting method essentially is intended to be used for a double-pole chip component. It, therefore, is difficult to apply the mounting method to the flip chip mounting. In addition, it also is difficult to apply the mounting method to electronic components with a number of electrodes formed with a narrow pitch. Hence, this mounting method is not suitable for a high density mounting.
In the method of mounting a chip component described in JP 3(1991)-241847 A, it is difficult to replace the chip component after the U-shaped cap is bonded to the circuit board. Moreover, the chip component tends to be misaligned with respect to the circuit board in bonding and fixing the cap. Particularly, when the electrodes are arranged with a narrow pitch, the yield decreases considerably.